The element with the symbol "Na" is sodium. Sodium is a highly reactive alkali metal and is essential for many biological functions. In its pure form, it is a soft, silvery-white, and very malleable metal. It is crucial for maintaining fluid balance in the body and is involved in nerve and muscle function. Sodium is commonly found in table salt, which is a compound made of sodium and chlorine (NaCl). Due to its reactivity, sodium is typically stored in oil or inert gases to prevent it from reacting with moisture in the air.